Borehole thermal energy storage for building heating application: A review

The utilization of solar energy and low-grade waste energy for building heating to reduce carbon emissions is an effective way to curb global warming. As a suitable approach for adjusting fluctuations between energy peaks and valleys, the borehole thermal energy storage (BTES) system can avoid diurnal and seasonal mismatches between the energy supply and demand for maximum energy utilization. Herein, operation principles and heat transfer model of the BTES system are reviewed, focusing on the configuration of the ground heat exchanger and the effect of thermal resistance on the heat transfer performance, concluding that the distribution of tubes is the main factor influencing the thermal resistance. This review highlights several ways to enhance the heat storage performance. The thermal storage density, heat transfer performance, and boundary insulation effect can be improved by adjusting the soil thermal properties, enhancing the backfill material performance, utilizing nanofluids, and upgrading boundary insulation. Subsequently, relevant application research based on BTES technology is reviewed, and the influences of system operating parameters and different materials on the system performance are examined from the experimental to application scales. Although the BTES system exhibits a long payback period, its operating costs and environmental benefits are excellent. Parameter sensitivity and coupling can be analyzed by numerical simulations, demonstrating that the BTES system can achieve a relatively stable temperature and high system performance in the long term. The results of this review are promising for achieving efficient BTES application.